<?php
$mub=$_GET["a"];
$mub2=$_GET["c"];
$com=$_GET["b"];
$result="";
if($com=="+")
    $result=$mub+$mub2;
else if ($com=="-")
    $result=$mub-$mub2;
else if ($com=="*")
    $result=$mub*$mub2;
else if ($com=="/")
    $result=$mub/$mub2;
?>

<form method="get">
    <input name="a" type="number"/>
    <select name="b">
        <option value="+">+</option>
        <option value="-">-</option>
        <option value="*">*</option>
        <option value="/">/</option>
    </select>
    <input name="c" type="number" />=
    <input name="d" type="number" value="<?php echo $result; ?>"/><br/>
    <button type="submit">计算</button>
</form>

